Summary

Aquatic and terrestrial crustaceans are dependent on both aerobic and anaerobic metabolism for energy production during exercise. Anaerobic energy production is marked by an accumulation of lactate in both muscle tissue and haemolymph, but the metabolic fate of lactate is not clear. Lactate recycling via gluconeogenesis and the potential role of carbonic anhydrase (CA) in supplying bicarbonate for the carboxylation of pyruvate were investigated in three species of decapod crustaceans: Callinectes sapidus (aquatic), Cardisoma guanhumi (semi-terrestrial) and Gecarcinus lateralis (terrestrial). CA activity was found in mitochondria and cytoplasmic fractions of gill, hepatopancreas and muscle of all three species. Significant activities of key enzymes of gluconeogenesis (e.g. pyruvate carboxylase, phosphoenolpyruvate carboxykinase and fructose bisphosphatase), however, could not be detected. Exercise to exhaustion produced a species-specific pattern of accumulation and clearance of lactate in tissue and haemolymph, indicating a differential degree of reliance on anaerobic energy production. Treatment with acetazolamide, a CA inhibitor, did not significantly alter the pattern of lactate dynamics in animals given repeated bouts of exhaustive exercise interspersed with periods of recovery. Injection of [U-14C]lactate resulted in the appearance of label in both muscle glycogen and excreted carbon dioxide, suggesting multiple metabolic fates for lactate. Lactate turnover rates for G. lateralis were similar to those reported for fish. In these animals, gluconeogenesis possibly proceeds via the reversal of pyruvate kinase, or via the typical Cori cycle but so slowly that the uncatalysed supply of bicarbonate is sufficient to keep pace with the low activities of pyruvate carboxylase and the subsequent low rates of pyruvate carboxylation.

Similar articles

Other journals from The Company of Biologists

Editor-in-Chief Hans Hoppeler and Monitoring Editor Craig Franklin highlight new initiatives at JEB in response to the COVID-19 pandemic. To continue advancing knowledge in the field, we are encouraging proposals for meta-analysis papers and timely Reviews and Commentaries within the JEB remit. New grant categories analogous to the Travelling Fellowships will fund collaborative data projects and the development of online resources for early-career researchers. Read their Editorial to find out more.

In their Review, Hanane Hadj-Moussa and Ken Storey assess OxymiRs in over 20 animal species. They reveal a lack of universal microRNA strategy, showing that instead there are species-specific responses to oxygen deprivation.

Researchers at nine institutions in Ireland can now publish an unlimited number of Open Access articles in JEB, immediately and at no cost to them, following a three-year Read & Publish agreement between The Company of Biologists and IReL. Find out more and see the growing list of participating institutions.

We are expanding the Conversation series to focus on the experiences of researchers out in the field. We’ll go behind the scenes as researchers tell us about their experiences on trawlers, in deserts, up mountains and in the remotest regions of the poles. Find out more about the series in the Editorial.

In the first interview, JEB author and editor Craig Franklin talks about the risks and challenges of working in remote areas with animals in their natural environment.